Composite foamed material

ABSTRACT

A composite foamed material and a process for the production thereof are disclosed herein, the process comprising premixing expandable or expanded polystyrene beads, a binder and fragments of resilient, open-celled neoprene. The materials are combined in the proportions of about 4-15% polystyrene beads, about 6-25% binder and about 60-90% open-celled neoprene. The combined materials are preferably compressed to a density of about 5-30 lbs. per cubic foot, more preferably 5-17 lbs. per cubic foot, and steam is applied to the compressed materials to cure the binder, and in certain embodiments to expand the polystyrene beads, thereby producing the desired composite foamed material.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to resilient cellular materials and moreparticularly to a composite foamed material.

2. Description of the Prior Art

A variety of cellular, and particularly foamed, materials are well knownin the prior art. Procedures for the production of such materials havecorrespondingly been known in the art, as well as procedures forproducing composite materials which include foamed or cellularmaterials. It is recognized that the advantage of a composite materialis that it typically displays physical properties which differ from theindividual components of the material. Further, the composite may beless expensive than an isolated material due to the inclusion ofrelatively inexpensive fillers. The present invention provides acomposite foamed material, and a process for the production thereof,having particularly advantageous physical characteristics for certainapplications.

In U.S. Pat. No. 3,300,421, issued to Merriman et al. on Jan. 24, 1967,there is disclosed a process for the production of "bonded resilientfragment" materials. The Merriam et al. patent discloses a process inwhich substantially rigid, pre-expanded glass or synthetic resinparticles are combined with resilient cellular material and a bondingagent. The cellular material is selected from natural rubber, syntheticrubber and polyurethane. The resultant mix is compressed whilesubstantial bonding occurs. The material produced by the process of theMerriman et al. patent is particularly adapted for certain applications.A cushioning material comprising a mixture of shredded pneumacel battingand shredded particles of polyurethane or rubber bonded together by anelastomeric binder is disclosed in U.S. Pat. No. 3,894,973, issued toYunan on July 15, 1975.

Generally, both of these patents and the other references fail toappreciate the significant finding of the present invention that acomposite of neoprene and polystyrene does not display substantialincrease in flammability or smoking over simply the neoprene material.These and all other references also fail to recognize that the minimalincrease in these characteristics is obtained while at the same timeadvantageous physical properties, particularly impact absorption, areachieved with a product which is less expensive than a pure neoprenematerial. Typical prior art for certain applications uses pure neoprene,while the present invention provides a composite material which is lessexpensive, displays greatly improved impact absorption properties, anddoes not exceed desired flame and smoke limitations.

In a particular aspect, the Merriman et al. procedure employs alreadyexpanded polystyrene granules, which granules are therefore uniform inshape. In contrast, the present invention includes in one embodiment theexpansion of polystyrene beads while under compression and while incombination with resilient cellular neoprene, and this producesirregularly-shaped, expanded beads. It has been found that, as a resultof this expansion of the polystyrene beads while commingled with thecellular material, a more intimate relationship between the twocomponents is achieved. For example, it has been observed that closelyspaced polystyrene beads, when expanded in the preferred embodiment inproximity with the existent cellular material, will trap portions of thecellular material therebetween, which would not result by the process ofthe Merriman et al. patent. In addition, the compression of the materialin accordance with the Merriman et al. patent tends to crush thepre-expanded polystyrene beads, whereas the expansion of the beads afterthe step of compression and in the presence of the existant cellularmaterial will tend not to produce "crushed" beads, but only to cause thebeads to expand in irregular fashion.

A number of other composite foamed materials have been proposed in theprior art. In U.S. Pat. No. 3,607,797, issued to Rubens et al. onSeptember 21, 1979, there is disclosed a composite foam having copolymerparticles dispersed throughout a urethane foam matrix. The compositefoam of the Rubens et al. patent is prepared by combining expandablecopolymer beads with a polyurethane foam precursor, and thereafterallowing the mixture to foam. Similar materials having thermoplasticbeads which are expanded with the surrounding and primarily supportingfoam material are disclosed in U.S. Pat. Nos. 3,878,133, issued toRubens on Apr. 15, 1975, and 2,958,905, issued to Newberg et al. on Nov.8, 1960. In U.S. Pat. No. 3,503,840, issued to Parrish on Mar. 31, 1970,there is disclosed a composite material having closed-cell reinforcingparticles supported within a surrounding foam matrix, the closed-cellparticles not being expanded with the foam matrix.

Einhorn et al. disclosed in U.S. Pat. No. 3,114,722, issued on Dec. 17,1963, a composite material comprising shredded cellular material bondedtogether by a prepolymer binder. Procedures for the production of foamedmaterials in which polystyrene beads are held together with a binder aredisclosed in U.S. Pat. Nos. 3,585,157, issued to Beck on June 15, 1971,and 2,959,508, issued to Graham et al. on Nov. 8, 1960. Additionalreferences in this art include the following: U.S. Pat. Nos. 3,855,049,issued to Klein on Dec. 17, 1974; 3,251,916, issued to Newnham et al. onMay 17, 1966; 2,892,216, issued to Steel on June 30, 1959; and2,878,153, issued to Hacklander on Mar. 17, 1959, as well as GreatBritain Pat. Nos. 1,033,702 issued to Oak and 889,278 issued to Taylor.

In none of these references is there described the expansion of thepolystyrene beads in situ with open celled material and bindermaintained under pressure. More generally, the present inventionachieves a product in another aspect which incorporates polystyrenematerial but which surprisingly does not have the disadvantageoussmoking and flammability characteristic of polystyrene.

SUMMARY OF THE INVENTION

In one aspect of the present invention there is provided a compositefoamed material, which comprises about 60-90% neoprene, about 4-15%polystyrene beads, and about 6-25% binder. Another aspect of the presentinvention provides a composite foamed material comprising the previouslymentioned materials in combination, the polystyrene beads being expandedseparately or in situ.

It is an object of the present invention to provide a composite foamedmaterial which is readily produced and is uniform in composition.

Another object of the present invention is to provide a composite foamedmaterial having novel and advantageous physical characteristics forparticular applications, particularly having minimal smoke and flameproperties.

It is a further object of the present invention to provide a compositefoamed material which may be produced by the utilization of relativelysimple and readily available blending and proportioning equipment.

Another object of the present invention is to provide a novel compositefoamed material having advantageous and uniform physical properties.

Further objects and advantages of the present invention will becomeapparent from the description of the preferred embodiment which follows.

BRIEF DESCRIPTION OF THE DRAWING

The FIGURE is a perspective view of a container useful as a mold inconjuction with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A number of isolated and/or composite foamed materials are known in theprior art, together with the various processes for the productionthereof. The present invention provides a simple and readily performedprocess for the production of a novel, composite foamed material havingparticularly advantageous physical properties for certain applications.The composite foamed material of the present invention is easilyproduced by the described process, and is particularly useful as acushioning or padding material, particularly for impact absorption.

In accordance with the process of the present invention, polystyrenebeads, a binder, and resilient open-celled neoprene are combinedtogether in a mix. The constituents may be combined in typical fashionwith available mixing devices. It has been found, however, that thepolystyrene beads and the binder, or alternatively the neoprene and thebinder, are preferably premixed and subsequently combined with the othermaterial.

The purpose for premixing these ingredients is that it is desirable toobtain a thorough and even distribution of the polystyrene beads withthe open-celled neoprene. It will be appreciated to one skilled in theart that a dispersion of the polystyrene beads in the open-celledneoprene alone is not obtainable since the polystyrene beads tend simplyto fall to the bottom of the mixing container, thus effectivelyseparating from the open-celled neoprene. Addition of the binder at thatpoint would effectively retain the separation to at least some degree.It has been discovered that by premixing the binder with the polystyrenebeads, a subsequent mixing with the fragmented, open-celled neoprenewill produce a uniform product since the polystyrene beads have beenevenly distributed within the binder. The binder and associated beadsbecome evenly distributed throughout the fragmented, open-celledneoprene. Alternatively, the beads may be added to a premix of theneoprene and binder also with suitable results.

Essentially any of the commercially-available, expandable or expandedpolystyrene beads may be utilized in the process of the presentinvention. Polystyrene beads are generally available as unexpanded, oras partially or fully expanded. The present invention encompasses theutilization of fully pre-expanded polystyrene beads, as well asunexpanded or partially pre-expanded polystyrene beads to the extentthat such beads would be further expandable. In the preferred embodimentdescribed below, the polystyrene beads are expanded in situ with thebinder and neoprene held under pressure. It is to be understood,however, that the novel and unexpected feature of desirably low smokeand flame properties may be obtained with the expansion of thepolystyrene beads either separately or in situ but without pressure, andthese embodiments are also intended to be covered hereby.

Expandable polystyrene beads are well known in the art. Such beadstypically comprise the polystyrene itself together with a blowing agentcomprising a volatile liquid such as a mixture of pentanes. Thepre-expanded polystyrene beads utilized in the present inventionpreferably have a maximum diameter of about 0.1 mm. A particular type ofpolystyrene bead found to be useful in the present invention is thatmarketed under the trademark Fostofoam by the Foster Grant Co., Inc.,Leominster, Massachusetts. The Fostofoam polystyrene beads are typicaland comprise 92-93% styrene and 6-7% blowing agent. Other expandablepolystyrene bead compositions are well known, and would be equallysuitable for use in the present invention.

The expandable polystyrene beads are preferably premixed with a suitablebinder for subsequent addition to the fragmented, open-celled neoprene.A substantial variety of suitable binders, also known in the art asbonding agents, are well known and equally useful in the presentinvention. Appropriate binders would include, for example, liquidpolyurethane-forming compositions, effecting the bonding by asingle-stage reaction or by an intermediate prepolymer reaction product.Other examples are the compositions based on liquid organic polysulfidestogether with epoxy resins. The suitability of various known binderswould be readily apparent to one skilled in the art, or would be easilydetermined by experimentation. It will be appreciated that the binder,upon curing or setting, should securely bond together the fragmentedopen-celled neoprene and the expanded polystyrene beads, whilepermitting the resulting material to be flexible.

A particular binder found to be useful in accordance with the presentinvention is that marketed under the trademark Mistabond 324-S by M-RPlastics & Coatings, Inc., Maryland Heights, Missouri. The Mistabond324-S is a urethane prepolymer binder which is a clear, amber liquidcomprising less than 10% methylene chloride and less than 15% toluenediisocyanate. Mistabond 324-S has a low viscosity and a high flashpoint,and displays excellent wetting characteristics. As will be furtherdescribed, the preferred process of the present invention utilizes theapplication of steam for curing or accelerating the binder and forexpanding the polystyrene beads, and it is therefore preferable that thebinder employed be steam-curable, although other binders such aswater-accelerated binders will work equally well with appropriatemodifications to the preferred process. It has also been noted thatadvantageous smoke and flame properties are achieved by the presentinvention, and the binder should therefore also be fire retardant.

The polystyrene beads and the binder, preferably after premixing of thetwo, are added to fragments of resilient, open-celled neoprene. Theopen-celled neoprene has been found to provide the desired smoke andflame properties in combination with the polystyrene beads. Moreparticularly, it has surprisingly been found that the composite materialincluding neoprene and polystyrene does not have substantially increasedflame or smoke properties over the neoprene alone. A typical use forproducts of the present invention is in school bus padding. Prior artproducts in such applications have included, for example, solelyneoprene in order to meet applicable state and/or federal specificationsfor such materials and even then these products have not beensatisfactory or have failed to meet the specifications. Applicant hasdiscovered that a composite product as described herein utilizing theexpensive neoprene in combination with relatively inexpensivepolystyrene beads meets the applicable standards. It is desired that theneoprene be open-celled since closed-celled materials are too resilientto provide an advantageous composite foamed material in accordance withthe present invention.

The constituents are combined in preselected proportions and theresultant mix is subsequently treated to yield the composite foamedmaterial of the present invention. The weight percentage of each of theconstituents in the final mix is from about 4% to about 15% ofpolystyrene beads, from about 6% to about 25% of the binder, and fromabout 60% to about 90% of the fragments of resilient, open-celledneoprene. In a most preferred embodiment of the present invention, theconstituents are combined in the proportions of about 7.5% ofpolystyrene beads, about 12.5% of binder, and about 80% of resilient,open-celled neoprene. It has been found to be preferable to include thebinder in an amount which is about 10% of the amount of the fragments ofresilient, open-celled neoprene in order to obtain proper and adequatebinding of the fragments in the resulting composite foamed material.

The materials are combined in the proportions recited above and they arebriefly mixed with appropriate equipment to insure a thoroughdistribution of the polystyrene beads and binder in relation to theresilient, open-celled neoprene. It will be appreciated that theresulting mixture initially in a fluffy mass. The mix is thentransferred to a container, such as container 10 in the FIGURE, forfurther processing. In accordance with the preferred embodiment of theprocess of the present invention, the mix of constituents is compressedwithin a mold to a density of from about 5 to about 30 lbs/ft³,preferably 5-17 lbs/ft³ and most preferably from about 7 to about 12lbs/ft³. The mix is compressed within a mold, such as container 10, andthen held in compression during the expansion of the polystyrene beadsand curing of the binder. Alternatively, the expansion of the beads isperformed separate of the other materials or in situ but withoutpressure.

Container 10 comprises a cart having a floor 12, end walls 13 and 14,and side walls 15 and 16. As will be further described below, side walls15 and 16 are hingedly mounted along their lower edges to floor 12, andare held in their initial, upright position by latches (not shown)securing them to the end walls. Caster wheels 11 are mounted to theunderside of floor 12 to facilitate movement of the container 10 forhandling purposes. A perforate plate 17 is mounted within container 10and above floor 12. A chamber 18 is defined by the volume surrounded byfloor 12, plate 17 and the side and end walls of container 10. Theconstituent mix is supported upon plate 17 during mixing, theperforations in the plate 17 being sufficiently small to prevent asignificant amount of material from passing downwardly through theplate.

When the constituent mix has been sufficiently blended in a suitableblending apparatus to obtain uniform distribution of the materials, thecontainer 10 is filled with a desired weight of material and thereafterpositioned to receive a second perforate plate 21. Plate 21 is securedto a piston rod 23 which is received within a hydraulic cylinder 22.Cylinder 22 is mounted appropriately to a surrounding structure, such asto the ceiling of a room, so that it may operate to apply a downward,hydraulic pressure through piston rod 23 to plate 21. With container 10positioned to receive plate 21, the plate is moved downwardly throughthe cooperation of hydraulic cylinder 22 and piston rod 23 to compressthe mix in the container to the desired extent.

It has been found particularly convenient to utilize pins 26 received inholes 25 in the endwalls of container 10 to regulate the final volume ofthe composite foamed material produced in accordance with the presentinvention. In accordance with this technique, a known amount of theconstituent mix is compressed to a certain extent, and the pins 26 areinserted in preselected ones of the holes 25. The plate 21 is thenpermitted to rise until it engages the pins 26, which pins then hold theplate in position during curing of the composite foamed material. Byappropriate positioning of the pins 26 in the holes 25, the volume andtherefore the density of the composite foamed material may bepredetermined. As previously indicated, the mix is compressed to adensity of from about 5 to about 30 lbs/ft³, preferably 5-17 lbs/ft³ andmost preferably from about 7 to about 9 lbs/ft³. In the latter instance,for the typical materials utilized in the present invention the initialmix is compressed to about 55% of its uncompressed volume.

With the mix held in compression in the preferred embodiment, thepolystyrene beads are expanded and the binder is cured. These steps mayboth be accomplished very readily by the application of steam to thecontainer 10. Coupling 19 connects steam line 20 to container 10 at alocation to be in communication with chamber 18. Line 20 is connected atits other end to a suitable source of steam. With the mix being held incompression between plates 17 and 21, steam is introduced through line20 and into chamber 18. The steam passes upwardly through theconstituent mix until it escapes through the perforations in plate 21.An insignificant amount of steam is lost through the holes 25 locatedbelow plate 21. By the passage of the steam through the mix, the binderis heated sufficiently to produce curing, and at the same time thepolystyrene beads are heated sufficiently to cause expansion. Steamcuring in this manner for a period of 2-5 minutes will generally producesufficient polystyrene bead expansion and binder curing to permitremoval of the composite foamed material, known as a bun. It has beenfound that typically the curing should be conducted for a limited timeperiod, perhaps not more than 3-4 minutes, to avoid deterioration orcollapse of the expanded polystyrene beads. The temperature of thecuring steam must be sufficiently low to avoid collapsing the beads. Ithas also been discovered that in performing the described process with acontainer 10, the described container is preferably made from metal dueto the high heat conductivity of the metal and the consequent avoidanceof channeling of the steam due to localized cooling of the steam. Thecontainer should also be preheated to avoid uneven heat distribution dueto the otherwise relatively cool container walls.

The binder is cured while the constituent mix is maintained undercompression. As is well known in the art, the binder may be cured to asubstantial extent while the material is in the mold, with further,final curing of the binder typically occurring after removal of the bunfrom the mold. It is of course preferable to provide for the bindercuring, while the material is in the mold, to an extent sufficient tocause the material to essentially retain its molded form and size. Thismay be accomplished by partial or full curing of the binder while in themold, with partial curing being preferred since it is sufficient and itreduces the period of time required for the bun to be retained in themold. Typically there is at least a slight expansion of the bun uponextraction from the mold as is to be expected. For the purposes herein,the term curing is used to mean curing of the binder at least to theextent sufficient to cause the bun to substantially retain its moldedsize and shape upon removal from the mold.

Upon sufficient curing of the binder and expansion of the beads, thecomposite foamed material is released from container 10. This isaccomplished by raising plate 21 and pivoting side walls 15 and 16 awayfrom the material, the side walls being hingedly mounted (not shown)along their bottom edge to floor 12. The composite foamed material isthereby made accessible and may be extracted from the container 10.

The following examples of the process and product of the presentinvention are given to further detail and exemplify the presentinvention, and are not intended to limit the invention herein disclosedand claimed.

EXAMPLE 1

A composite foamed material was prepared in accordance with the methodof the present invention. To 25 lbs of the binder Mistabond 324-S wasadded 15 lbs of Fostofoam polystyrene beads. The binder and beads werethoroughly mixed and then added to 160 lbs of shredded neoprene foam,representing weight percentages of the constituents to the finalmaterial of 12.5% binder, 7.5% beads and 80% neoprene foam.Alternatively, the neoprene and binder were blended together first forabout one minute, and the beads were then added and the mixture blendedabout two minutes.

The materials were mixed well and then placed under compression in acontainer as shown in FIG. 1. The container was dimensionedapproximately 72 in×38 in×14 in with the second perforate plate loweredto compress the mix, equivalent to a volume of about 22.2 ft³ and adensity for the 200 lbs of material of about 9 lbs/ft³. Steam wasintroduced through the container for about 3 minutes to expand the beadsand accelerate or cure the binder. The resultant bun was removed fromthe container after cooling about 30 minutes and yielded a compositefoamed material displaying excellent impact absorption, flame and smokecharacteristics.

EXAMPLE 2

The procedure of Example 1 was followed except that the materials wereadded in the proportions of 25 lbs of binder (9.6%), 30 lbs of beads(11.4%), and 207 lbs of scrap foam (79%). The resultant composite foamedmaterial displayed excellent physical properties.

EXAMPLES 3-8

The procedure of Example 1 was followed except the amount of binder waschanged in one procedure to 50 lbs and in another to 12.5 lbs. In twoadditional procedures the method of Example 1 was followed except theamount of beads in one instance was 30 lbs and in the other was 7.5 lbs.The procedure of Example 1 was also repeated exactly except for changingthe amount of neoprene in one instance to 60 lbs and in another instanceto 360 lbs. Each of the resultant materials displayed good physicalcharacteristics.

EXAMPLES 9-11

The procedure of Example 1 was followed except the materials werecompressed, in four different procedures, to about 5, 7, 17 and 30lbs/ft³. Materials showing good physical properties were produced,although the materials in the density range of 7-9 lbs/ft³ displayed thebest physical characteristics with respect to impact absorption. Thesephysical properties of the material are readily and accuratelyascertainable by standardized test procedures, and the suitability ofthe material for various applications may thereby be determined.

EXAMPLES 12-13

The procedure of Example 1 was followed except that the polystyrenebeads were pre-expanded separately or in situ and the binder was thencured with the indicated, applied pressure. Materials of good physicalproperties were produced.

EXAMPLES 14-16

Specifications currently exist in California relating to the non-burningqualities for seat cushions. The federal government and potentiallyother states are nearing the adoption of similar regulations. Materialsproduced as described herein were therefore tested under existing smokeand flame test procedures.

A flammability test described under ASTM Standard E 162-75 wasperformed. This test uses a 12 in. by 18 in. radiant heat source panelin front of which is placed a 6 in. by 18 in. specimen. The specimen isinclined at 30° with ignition forced to occur near the upper edge andthe flame front progressing downward. The 1 inch thick specimen isprepared by predrying it at 140° F. for 24 hours and then equilibratingit at 73° F. and 50% relative humidity. The material in four separatetests had flame spread indexes, which is a combined measure of the rateof progress of the flame front and the rate of heat liberation from thematerial, of 7. By comparison, the flame spread index for a commercialneoprene product sold under the trade name Koylon was measured asbetween 3.5 and 5.6. In a related test, the material of the presentinvention was compared with the same product except without thepolystyrene beads. It was found that the flame spread index increasedonly from 5.4 to 5.9 when the polystyrene beads were present.

A smoke density test was also conducted in conformance with NFPAStandard 258-76. This test measures the smoke generated by a 3 in.×33in. specimen exposed to a radiant energy source under flaming andnon-flaming conditions. The specimen was prepared as for theflammability test and the results showed a smoke generation average of506 for the flaming mode tests and of 575.7 for the non-flaming modetests.

Impact absorption tests were also conducted on the composite material.It is an advantage of this material that desired impact properties areachieved by the presence of the polystyrene beads. Standard tests forbus padding were conducted by impacting samples with an object ofpredetermined and standardized configuration and weight, at a speed of16.1 feet per second. Typical resisting forces were measured in therange of 27.62 pounds to 48.00 pounds, acceptable values underapplicable use standards.

What is claimed is:
 1. A flame-resistant composite foamed materialcomprising:a. fragments of resilient, open-celled neoprene; b. expandedpolystyrene beads dispersed among said fragments of open-celledneoprene; and c. a binder securing together said fragments ofopen-celled neoprene and said beads, said open-celled neoprene, beadsand binder being present in amounts of about 60% to about 90% of theopen-celled neoprene, about 4% to about 15% of the beads, and about 6%to about 25% of the binder, said composite foamed material having adensity of from about 5 to about 30 lbs/ft³.
 2. The material of claim 1and having a density of from about 5 to about 17 lbs/ft³.
 3. Thematerial of claim 1 and comprising about 80% of the resilient,open-celled neoprene, about 7.5% of the polystyrene beads and about12.5% of the binder.
 4. The material of claim 1 in which the amount ofthe binder is about 15% of the amount of said resilient, open-celledneoprene.
 5. The material of claim 1 in which said beads are expanded insitu while said open-celled neoprene and said beads dispersed thereinare held under compression.
 6. The material of claim 5 in which theamount of the binder is about 15% of the amount of said resilient,open-celled neoprene.
 7. The material of claim 5 in which thepolystyrene beads have a maximum diameter of about 0.1 mm prior toexpansion.
 8. The material of claim 5 in which said beads were expandedin situ and said binder was cured to provide securement together of saidfragments of open-celled neoprene and said beads by the passage of steamthrough a mixture of said open-celled neoprene, unexpanded beads andbinder.
 9. The material of claim 8 and having a density of from about 5to about 17 lbs/ft³.
 10. The material of claim 8 and comprising about80% of the resilient, open-celled neoprene, about 7.5% of thepolystyrene beads and about 12.5% of the binder.